Three-dimensional four-dimensional in the medical field refers to three-dimensional color ultrasound and four-dimensional color ultrasound, the difference between them is that the dimension is different, the presentation form is different, the function is different and so on. 1. Different dimensions: three-dimensional ultrasound is based on two-dimensional ultrasound, plus three-dimensional stereo images, which can see the growth of the fetus, changes in the placenta, amniotic fluid and umbilical cord, and can detect fetal malformations. Four-dimensional ultrasound is based on three-dimensional ultrasound, added the concept of time, can be presented in real time the dynamic activities of the fetus, you can clearly observe the baby’s voice and smile. 2. Presentation form is different: in layman’s terms, three-dimensional color ultrasound is a picture, is static, and four-dimensional color ultrasound is a dynamic image, than three-dimensional color ultrasound three-dimensional effect is better, you can see more details, observation is more detailed, clear. 3. Functions are different: three-dimensional color ultrasound mainly observes the internal organs with or without abnormalities and excludes structural deformities. Four-dimensional color ultrasound can also check the function of the motor nervous system and the coordination of movement. Three-dimensional four-dimensional are to let the doctor see more clearly, if three-dimensional four-dimensional can be used together, can improve the accuracy of the examination.